A direct modeling approach to momentum, heat and mass exchange at the ocean-atmosphere interface at high wind speed

为了更好地预测对人类活动有巨大影响的极端天气事件，如热带气旋的增强，更好地了解在极高风速下海洋-大气界面的动量、热量和质量交换是必要的。考虑到这些两相湍流的复杂性，建模工具对于揭示详细的物理机制非常有价值。该研究将为高风速下的空气-水全耦合模拟提供一个新的计算框架，包括破碎波、湍流风、液滴的产生及其对湍流波边界层热交换和质量交换的影响。对单个破碎波和液滴演化的小尺度动力学的初步研究将提供给一个更大尺度的模型，该模型能够解决为小尺度模型提供强迫背景的流动。这种综合方法将导致简化模式和参数化的普遍改进，可以在从高分辨率模式到更大尺度地球系统模式的广泛数值工具中实施和测试，从而导致气候和天气预报的改进。该项目将使普林斯顿大学的本科生和研究生接触到关键的环境挑战，这些挑战需要研究基本的多相流，并通过研讨会和教学活动促进开源方法的使用。海气相互作用的大范围尺度将被分成两组更容易处理的问题。第一部分将考虑液滴在空气中的蒸发，充分解决液滴喷射和与周围空气的热交换问题，以求解湍流边界层强迫下的风浪破碎动力学。这种高保真模拟将跨越100微米到1m的尺度，重点了解靠近水面的强风强迫湍流与水滴之间的小尺度耦合，直接求解高风速下的热质交换、波滴过程以及热动量交换的耦合。为这些小规模过程开发的模型将集成到一个多层数值框架中，类似于大涡模拟。这样的模拟将能够解决从1米到1公里范围内的真实破碎波统计数据，从而可以表示湍流的外部尺度。对热量和动量收支的分析将有助于理解当前整体公式中的不确定性，并可能导致适用于用于热带气旋增强研究的更大尺度模型的热量和阻力系数的新参数化。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

A better understanding of exchange of momentum, heat, and mass at the ocean-atmosphere interface at very high wind speed is necessary to better predict extreme weather events, which have dramatic impact on human activities, such as tropical cyclone intensification. Given the complexity of these two-phase turbulent flows, modeling tools are extremely valuable to unravel the detailed physical mechanisms. This research will provide a novel computational framework for fully coupled air-water simulations at high wind speed, including breaking waves, turbulent wind, droplet generation and their influence on the heat and mass exchange in the turbulent wave boundary layer. The initial work on the small-scale dynamics of individual breaking waves and droplet evolution will feed into a larger-scale model able to resolve the flows that provide the forcing context for the small-scale model. This comprehensive approach will lead to a general improvement in simplified models and parameterization, that can be implemented and tested in a wide range of numerical tools, from high resolution models to larger scale Earth system models, leading to improvement in climate and weather forecast. This project will expose undergraduate and graduate students at Princeton to critical environmental challenges that require research on fundamental multi-phase flows, and promote the use of open-source methods, through workshop and teaching activities.The large range of scales involved in air-sea interaction will be split into two sets of more tractable problems. The first will consider droplet evaporation in the air, fully resolving droplet ejection and heat exchange with the surrounding air for wind-wave breaking dynamics forced by turbulent boundary layer. Such high-fidelity simulations will span scales from 100 microns to 1m and focus on understanding the small-scale coupling between high wind forced turbulence close to the water surface and droplets, directly solving for heat and mass exchange, waves and droplets processes and the coupling of heat and momentum exchange at high wind speed. The models developed for these small-scale processes will be integrated into a multi-layer numerical framework, akin to large eddy simulations. Such simulations will be able to resolve realistic breaking wave statistics spanning scales from 1m to 1km, allowing to represent the outer scales of the turbulent flow. Analysis of the heat and momentum budget will help understand current uncertainties in bulk formulation and may lead to new parameterizations for the heat and drag coefficient applicable to larger scale models used for tropical cyclone intensification studies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.